This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for non-passerines

Lynx Edicions and BirdLife International will soon publish the HBW-BirdLife Illustrated Checklist of the Birds of the World, building off the Handbook of the Birds of the World series, and BirdLife’s annually updated taxonomic checklist.

The new Checklist will be based on the application of criteria for recognising species limits described by Tobias et al. (2010). Full details of the specific scores and the basis of these for each new taxonomic revision will be provided in the Checklist.

Following publication, an open and transparent mechanism will be established to allow people to comment on the taxonomic revisions or suggest new ones, and provide new information of relevance in order to inform regular updates. We are also actively seeking input via a discussion topic here regarding some potential taxonomic revisions that currently lack sufficient information.

The new Checklist will form the taxonomic basis of BirdLife’s assessments of the status of the world’s birds for the IUCN Red List. The taxonomic changes that will appear in volume 1 of the checklist (for non-passerines) will begin to be incorporated into the 2014 Red List update, with the remainder, and those for passerines (which will appear in volume 2 of the checklist), to be incorporated into subsequent Red List updates.

Preliminary Red List assessments have been carried out for the newly split or lumped taxa. We are now requesting comments and feedback on these preliminary assessments.

White-throated Eared-nightjar Eurostopodus mystacalis is being split into E. mystacalis, E. exul and E. nigripennis, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, E. mystacalis (BirdLife species factsheet) was listed as Least Concern on the basis that it was not thought to approach the thresholds for Vulnerable under any of the IUCN criteria. This species was estimated to have an extremely large range, and hence did not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence of less than 20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appeared to be decreasing, the decline was not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (at least a 30% decline over ten years or three generations). The population size has not been quantified, but it was not believed to approach the thresholds for Vulnerable under the population size criterion (fewer than 10,000 mature individuals with a continuing decline estimated to be at least 10% over ten years or three generations, or with a specified population structure).

E. exul is known only from north-western New Caledonia, where a single specimen was collected from ‘coastal flats’ in 1939 (Mayr 1941 in del Hoyo et al. 1999, Holyoak 2001). The species is thought to be extinct (Dutson 2011), but is very poorly known, and is perhaps best classed as Critically Endangered (Possibly Extinct), as suggested by Szabo et al. (2012). This listing is suggested under criterion D1, on the basis that, if it is still extant, there are likely to be fewer than 50 mature individuals remaining, given that it is known from just one specimen.

E. nigripennis is endemic to Bougainville and the Solomon Islands, where it occurs in coastal habitats, such as beaches and offshore islets (del Hoyo et al. 1999, Holyoak 2001). It is suggested that it qualifies as Vulnerable under criterion C2a(i), on the basis that it is estimated to number fewer than 2,500 mature individuals, given its apparent rarity (Holyoak 2001), with all subpopulations thought to number fewer than 1,000 mature individuals (but all or most subpopulations deemed likely to exceed 250 mature individuals), and an on-going decline is inferred based on a decreasing frequency of records (Dutson 2011) and the likely threat of disturbance to beaches.

E. mystacalis (as defined following the taxonomic change) is widely distributed in eastern New Guinea and eastern Australia, where it uses a variety of habitats, including modified areas (del Hoyo et al. 1999, Holyoak 2001). It is likely to warrant classification as Least Concern on the basis that it is not thought to approach the thresholds or Vulnerable under any of the IUCN criteria.

Comments are invited on these suggested categories and further information would be welcomed.

I have only once heard E. nigripennis in many months of fieldwork across the Solomon Islands, have obtained reliable records from local people only at Tetepare island and nearby Hele Bar, and have had reports from western birders only at Tetepare island. As such, although it is very poorly-known, I support the proposed categorisation. (However, i suggest that few subpopulations number >250 mature individuals.)

Nests of E. nigripennis have been recorded on Tetepare at Kaife, Kororo, Saromana and Nabonibao beaches, suggesting that the island, which is uninhabited, unlogged and has an area of 11,880 ha, may be important for the species. The beaches are occasionally used by pig hunters and other visitors and there may be some disturbance to nests – in one instance the parent bird was flushed and a chick was then killed by invasive fire ants.

There are apparently no recent published records away from Tetepare (eg. none from Bougainville since the 1930s).

Incidence of egg-harvesting on the island is believed to be low, but eggs of Island Imperial-pigeon, Black-naped Tern and Great Crested Tern have been harvested by landowners or visitors.

Further to the posting of this discussion topic, please note the IUCN guidelines for defining Possibly Extinct taxa:

“Critically Endangered (Possibly Extinct) taxa are those that are, on the balance of evidence, likely to be extinct, but for which there is a small chance that they may be extant. Hence they should not be listed as Extinct until adequate surveys have failed to record the species and local or unconfirmed reports have been investigated and discounted. ‘Possibly Extinct in the Wild’ correspondingly applies to such species known to survive in captivity.

Note that ‘Possibly Extinct’ is a tag, and not a new Red List Category.

Different standards of evidence are required from assessors when deciding to assign a taxon to the Extinct or Critically Endangered (Possibly Extinct) categories. Assignment to the Extinct category requires evidence beyond reasonable doubt that the last individual of the taxon has died. Assignment of the ‘Possibly Extinct’ tag requires that on the balance of evidence, the taxon is likely to be extinct, but there is a small chance that it may be extant. Relevant types of evidence supporting a listing of extinction include (Butchart et al. 2006):
• For species with recent last records, the decline has been well documented.
• Severe threatening processes are known to have occurred (e.g., extensive habitat loss, the spread of alien invasive predators, intensive hunting, etc.).
• The species possesses attributes known to predispose taxa to extinction, e.g. flightlessness (for birds)
• Recent surveys have been apparently adequate and appropriate to the species’ detectability, but have failed to detect the species.

Such evidence should be balanced against the following considerations (Butchart et al. 2006):
• Recent field work has been inadequate (any surveys have been insufficiently intensive/extensive, or inappropriately timed; or the species’ range is inaccessible, remote, unsafe or inadequately known).
• The species is difficult to detect (it is cryptic, inconspicuous, nocturnal, nomadic, silent or its vocalisations are unknown, identification is difficult, or the species occurs at low densities).
• There have been reasonably convincing recent local reports or unconfirmed sightings.
• Suitable habitat (free of introduced predators and pathogens if relevant) remains within the species’ known range, and/or allospecies or congeners may survive despite similar threatening processes.

Similar considerations apply when assigning a taxon to either the Extinct in the Wild or Critically Endangered (Possibly Extinct in the Wild) categories.”